The present invention relates to a turbine cooling apparatus applicable to a torque tube section that is used to supply cooling air for moving blades of a high-temperature gas turbine from a stationary system to a rotating system (rotor) after the air is extracted from a compressor.
FIGS. 1 and 2 show a conventional gas turbine cooling apparatus. A cylindrical torque tube 2 is coupled coaxially to one side a turbine disk 6 that has a plurality of moving blades 7. The inner surface of the central portion of the disk 6 is thick and stepped. An air separator 1 is fitted on the tube 2 so that its inner surface is in contact with the outer surface of the tube 2. Formed between the separator 1 and the torque tube 2 is a passage a through which cooling air is supplied to the moving blades 7. An intermediate shaft cover 5, having a cavity 5a therein, is put on the outer surface of the separator 1. The cover 5 is connected to a cooling air supply pipe 4. In FIG. 1, numeral 10 denotes a spindle bolt.
In this arrangement, the moving blade cooling air is fed from the cooling air supply pipe 4 to a rotating-side passage a via the cavity 5a. Then, the cooling air is delivered to the moving blades 7 through holes in the disk 6.
As shown in FIG. 1, the air separator 1 has a very thin wall, while the torque tube 2 has a thick-walled portion. Accordingly, there is a substantial difference in thermal capacity between these two members.
During actual-load operation with the operation pattern shown in FIG. 3, the ambient temperature around the air separator 1 is stable, so that the respective temperatures of the separator and the torque tube are constant, as shown in FIG. 4. When the ambient temperature changes, especially when the turbine is stopped, cold air passes through the air separator. Owing to the aforesaid difference in thermal capacity, therefore, the transient metal temperature change varies. Accordingly, the air separator and the torque tube are differently deformed by heat, that is, there is a substantial difference in deformation between them. Possibly, this difference may exert a bad influence on the gas turbine.